    <div class="refentry" id="atan">
      <div class="titlepage"></div>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>atan — return the arc-tangent of the parameters</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>Declaration</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">genType <strong class="fsfunc">atan</strong>(</code>
              </td>
              <td>genType <var class="pdparam">y</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>genType <var class="pdparam">x</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">genType <strong class="fsfunc">atan</strong>(</code>
              </td>
              <td>genType <var class="pdparam">y_over_x</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>y</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the numerator of the fraction whose arctangent to return.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>x</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the denominator of the fraction whose arctangent to return.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>y_over_x</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specify the fraction whose arctangent to return.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            <code class="function">atan</code> returns the angle whose trigonometric arctangent is
            <math overflow="scroll">
                <mfrac>
                    <mrow>
                        <mi mathvariant="italic">y</mi>
                    </mrow>
                    <mrow>
                        <mi mathvariant="italic">x</mi>
                    </mrow>
                </mfrac>
            </math> or <math overflow="scroll"><mi mathvariant="italic">y_over_x</mi></math>,
            depending on which overload is invoked. In the first overload, the signs of <math overflow="scroll"><mi mathvariant="italic">y</mi></math>
            and <math overflow="scroll"><mi mathvariant="italic">x</mi></math> are used to determine the quadrant
            that the angle lies in. The values returned by <code class="function">atan</code> in this case are in the range
            <math overflow="scroll">
                <mfenced open="[" close="]">
                    <mrow>
                        <mo>−</mo>
                        <mi>π</mi>
                    </mrow>
                    <mi>π</mi>
                </mfenced>
            </math>. Results are undefined if <math overflow="scroll"><mi mathvariant="italic">x</mi></math> is zero.
        </p>
        <p>
            For the second overload, <code class="function">atan</code> returns the angle whose tangent is
            <math overflow="scroll"><mi mathvariant="italic">y_over_x</mi></math>. Values
            returned in this case are in the range
            <math overflow="scroll">
                <mfenced open="[" close="]">
                    <mrow>
                        <mo>−</mo>
                        <mfrac>
                            <mi>π</mi>
                            <mn>2</mn>
                        </mfrac>
                    </mrow>
                    <mfrac>
                        <mi>π</mi>
                        <mn>2</mn>
                    </mfrac>
                </mfenced>
            </math>.
        </p>
      </div>
      {$pipelinestall}{$examples}
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">

            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="3">
                <span class="bold"><strong>OpenGL ES Shading Language Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>1.00</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.00</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.10</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">atan</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="sin"><span class="citerefentry"><span class="refentrytitle">sin</span></span></a>,
            <a class="citerefentry" href="cos"><span class="citerefentry"><span class="refentrytitle">cos</span></span></a>,
            <a class="citerefentry" href="tan"><span class="citerefentry"><span class="refentrytitle">tan</span></span></a>,
            <a class="citerefentry" href="asin"><span class="citerefentry"><span class="refentrytitle">asin</span></span></a>,
            <a class="citerefentry" href="acos"><span class="citerefentry"><span class="refentrytitle">acos</span></span></a>
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright © 2011-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.
        </p>
      </div>
    </div>
